The aggregation of two (or more) lower bandwidth asynchronously clocked communication links into a higher bandwidth link is required in many situations. Non-limiting examples of lower bandwidth asynchronously clocked packetized communication links include AAL1 UDT (Asynchronous Transfer Mode Adaptation Layer Type 1 User Datagram Protocol Data Transfer Protocol) or PWE3 SAToP (Pseudowire Emulation Edge-To-Edge Working Group Structure-Agnostic Time-Division Multiplexing over Packet) links being carried via a gigabit Ethernet (IEEE 802.3) or other high speed serial data connection.
In such situations, the asynchronous nature of the arriving packets creates periodic congestion on the higher bandwidth link when the lower bandwidth links all attempt to transmit their packets through the higher bandwidth link at exactly the same instant. The periodic congestion occurs at a beat frequency of Fbeat=F0−F1 where F0 and F1 are the packet frequencies of the lower bandwidth links. This periodic congestion at frequency Fbeat is low frequency noise which is difficult to filter out in the buffer adaptive clock recovery circuits.